Arrangement for printing photographs



Sept. l2, l933.-

' ARRANGEMENT FOR PRINTING PHOTOGRAPHS Filed Jan. 6, 1930 lll A. NAUMANN1,926,596

Patented Sept. 12,

mRANGEMEN'r Fon PRINTING PHOTOGRAPHS Arthur Naumann, Berlin, Germany,assignor to Voigtlander & Schn Aktiengesellschaft, Braunschweig,Germany, a joint stock comj pany of Germany Application January 6, 1930,Serial No. 418,825, and in Germany November 9, 1929 9 Claims. (Cl.95-'73) This invention relates to a method and arrangement for printingphotographs, which includes the printing from negatives on gaslightandsilver-bromide paper, the printing of diapositive plates, the printingof positive cinematographic lms from negatives, the making ofenlargements on silver-bromide paper, and the like. All these kinds ofprinting are referred to in the following description as the printing of10 photographs or negatives.

The feature of thisinvention consists in determining and obtaining theproper intensity of electric light necessary for printing of anyparticular photograph or negative with a certain k constant lightingduration. The method .em-

ployed for setting the lamp to the proper intensity consists indetermining the density of the negative to be copied on a density screenwith the aid of a density measuring apparatus and in positively andautomatically regulating, when adjusting the density screen, theeffective value of a series resistance included in the electric circuitof the lamp, so that it iniiuences the lamp in proportion to the densitymeasurement. In the use of this resistance-regulating apparatus thenegative to be copied and a density screen are observed simultaneouslythrough an eye-piece, and the density screen is adjusted until a degreeof density is observed on the screen corresponding to that of thenegative, that is until the degree of density observed on the screen isthe same as the degree of density observed on the negative. By theadjustment of the density screen a sliding contact is shifted on avariable resistance. This variable resistance and the sliding contactare included in the electric circuit o! the copying lamp, and theintensity or the light alters with the shifting of the sliding contacton the variable resistance. The parts are so proportioned that the valueof the resistance thus made eiective in the light circuit variesinversely with the density of the negative: the greater the density, theless the resistance, and consequently the greater the intensity oi thelight. Instead of acting directly on the resistance by means of asliding contact, the density `screenniay act upon an oscillatableadjusting lever which, on being oscillated, slides over contactsarranged side by side at suitable distances apart and connected to thewindings of the resistance. This adjusting lever is also provided with asliding contact, and this contact as also the resistance are connectedto the circuit oi the lamp.

Two embodiments of the invention are illustrated hy way of example inthe accompanying drawing in which Fig. l. shows in front elevation theresistanceregulating apparatus, and, diagrammatically, the lamp and thelamp circuit with which the resistance-regulating apparatus isassociated.

Fig. 2 is a cross section of Fig. l.`

Fig. 3 shows a modied form of construction in iront elevation,

Like parts are indicated by the same reference letters in each of thediierent gures of the drawing.

A known apparatus is used for measuringr the density of the negative andconsists of a tube a with an extension i and an eye-piece c in thecentre portion and two tubular pieces d and e projecting at rightangles, one from each end of the tube a. By means of an angular mirror,t and two mirrors g and h, arranged one in each of the two tubularpieces, it is possible to look simultaneously through the two tubularpieces d and e. This piece of apparatus is conveniently mounted in asuitable stationary support ar. The negative 'i is placed in a seatformed in the support :1: tc receive it and in a position in front of sathe tubular piece d, and a movable gauge, for example, a density screenis is adjustably borne on a stationary support in :front of the tubularpiece e. The density screen is is composed of transparent strips paintedgrey in absolutely uniformly 35, increasing degrees of densitycorresponding to the degrees of density occurring in negatives. Suchdensity screens are known under the name of grey wedge. The holder. ofthe density screen is slidable in guides y in its stationary support;and in operation, when measuring the density of a negative, it isadjusted to such position that the degree of density visible in theeyepiece c corresponds with the density of the negative which, is alsovisiblein the eye-piece. 95

In so adjusting the density screen, the negative 'i and the screen k aresimultaneously illuminated in equal degree by light from any suitableand convenient source. When considering the drawing, it .may beunderstood that negative and screen are, on the left (Fig. 2),` exposedto diffused sunlight, and that it is sunlight which, transmitted throughthem, is received through eye-piece c.

Associated with this density-measuring apparatus, means are provided foradjusting the intensity ofthe light emitted by the lamp of the printingapparatus. In the drawing this lamp o and its circuit arediagrammatically indicated. The printing apparatus is not otherwiseshown;

it may be understood to be of usual character and to include, Within abox or other dark chamber, and in association with the lamp, suitablesupport for the negative and for the paper or other carrier withsensitized surface, upon which printing is to be effected.

The holder lof the density screen carries a sliding contact m on itsunder side, which contact slides on a series resistance n, and thiscontact as it slides brings into the electric circuit of the copyinglamp o a greater or less quantity of resistance. A certain intensity oflight with a certain duration is required, according to the density ofthe negative. The intensity of the lamp alters with the displacement ofthe sliding contact m on the resistance, and the resistance is such thatthe intensity of the lamp is always adapted to the degree of density ofthe negative-being adjusted in adjustment of the density screen. Thus,if the degree of density of the screen in the measuring apparatus isproperly set to correspond with that of the negative, the negative canbe exposed under the lamp with the proper intensity of light. Theduration of the exposure (the intensity of the light being constant) isdependent upon the printing material used and upon the density of thenegative, and the determining of the suitable length of exposure for thedensity of the negative is much more diiiicult and unpractical thank(the duration of the time of exposure being constant) is thedetermination of a suitable intensity of the printing light inthe mannerdescribed. A length of exposure suitable for the particular kind ofprinting paper to be used, and also the conditions existing in theapparatus above described, are predetermined and permanently preserved.A uniform length or exposure will always be maintained by means of acontrol clock p connected to the lamp circuit.

In use, the negative from which the print is to be made is firstintroduced into the resistanceadjusting apparatus and there becomes thedetermining factor by means of which the light circuit is brought tocondition to afford, when the lamp is illuminated, light of properintensity. When this has been done, the negative is removed from itsposition in the resistance-adjusting apparatus and introduced into theprinting apparatus, in proper relation to the lamp and to the paper orother surface to be printed. The light circuit then is completed andlight of an intensity so adjusted continues until, by the operation ofthe stop clock p, its circuit is broken again.

In the form of construction shown in Fig. 3 the holder Z of the densityscreen k acts on an adjusting switch q oscillatable around a pivot pin rand in oscillating causes its sliding contact. s to slide over contactterminals t, each of which is conductively connected with the seriesresistance n. The centre terminal t is connected with the centre of theresistance coil, and the terminals on each side are connected with theresistance coil at points on each side of the centre at properly spacedintervals. The adjustable holder Z of the density screen may act on theadjusting switch q in any suitable manner. According to the exampleillustrated a pin u, arranged on the holder l of the density screen andwhich may have a ball head atits end, engages in atubular extension o ofthe adjusting switch. In displacing the density screen when settingsameto the density of the negative, the pin u engages the regulatingswitch q on its neck part o and swings it accordingly, causing therebythev sliding contact to slide over the contacts t and to be set to oneof same. By this means the eiective length of the resistance n, throughwhich the lamp current ilows, is so adjusted that the lamp has theintensity necessaryfor printing the negative, the density of which hasbeen measured by the apparatus.

I claim:-

l. A system for printing photographs comprising in combination anapparatus with two openings for measuring the density of the negative, adensity gauge, the negative to be printed and the said gauge beingplaced each in front'of one of said openings ofv the apparatus, anadjustable holder for the gauge, a sliding contact on said holder, anelectric lamp, and a series resistance, said sliding contact and saidseries resistance being connected to the electric circuit of said lamp,and said sliding contact adapted to slide on said series resistance.

2. A system for printing photographs, comprising in combination anapparatus with two openings for measuring the density of the negative, adensity gauge, the negative and said gauge being placed each in front ofone of said openings of the measuring apparatus, an adjustable holderfor said gauge, a sliding switch, said holder acting on said slidingswitch, an electric lamp, a lamp-energizing circuit, a resistance coilarranged in said circuit and in series with said lamp, said slidingswitch being also included in said circuit and being movable tosuccessive positions of contact at intervals along the windings of saidresistance coil.

3. A system for printing photographs, comprising in combination anadjustable apparatus for measuring the density of lthe negative, asource of light, means connected up in the circuit of said source oflight and movable in response to adjustment of said density-measuringapparatus for adjusting the intensity of said source of light to thedensity of such negative, and a switch watch also connected up in thecircuit of said source of light.

4. A system for regulating the active light intensity for photographicprinting, comprising an instrument for visually ascertaining the densityof the negative to be printed, a source of light, and means operativelyconnected with said instrument for regulating the active light intensityof said source of light.

5. A system for regulating the active light intensity for photographicprinting, comprising an instrument for Visually ascertaining the densityof the negative to be printed, a source of light, and means operativelyconnected with said instrument for regulating lthe intensity of thelight emitted from the said source.

6. A system for regulating the active light intensity for photographicprinting, comprising an instrument for visually ascertaining the densityof the negative to be printed, an electric lamp and its circuit, andmeans operatively connected with said instrument for regulating thecurrent supplied to said lamp.

'7. A system for regulating the active light intensity for photographicprinting, comprising an instrument for visually ascertaining the densityof the negative to be printed, an electric lamp and its circuit, andmeans directly connected with said instrument for regulating the currentsupplied to said lamp.

8. A system for regulating the active light ininstrument for visuallyascertaining the density llil of the negative to be printed, a source oflight, means operatively connected with said instrument for regulatingthe active light intensity of said source of light, and time-controlledmechanism for throwing said 'source of light out of operation.

ARTHUR NAUMANN.

